Ultratrace elements requirements

The ultratrace element requirements of animals (and men) are, in part, extremely low and are reliably met everywhere. In practice, symptoms of ultratrace element deficiency in animals and man do not occur, apart from genetic defects which prevent utilization of the ultratrace elements. Hints as to the biological essentiality of these elements were only obtained in experiments with semisynthetic rations that where extremely poor in the element(s) to be tested. These conditions led to depressed performances, deficiency diseases, and reduced life expectancy. Deficiency symptoms of ultratrace elements were not registered in real life, as the... 

The essential mineral nutrients are classified either as principal elements or as trace and ultratrace elements. The distinction between these groups is the relative amounts ia the dietary requirement (see Table 1). 

Generally, extensive prior information is known about the sample in terms of the elemental composition and in these cases methods of analysis can be selected that will provide the desired result. However, if this information is not available or else a more general survey of ultratrace elements is required, then AES with an inductively coupled plasma source is the only atomic spectrometric technique that can provide these data at ultratrace levels. 

LA-ICP-MS was used for in situ determination of ultratrace elements in quartz. The analytical protocol included the following elements Al, Ba, Be, Cr, Ee, Ge, K, Li, Mg, Mn, Pb, Rb, Sr, Th, Ti and U . Apphcation of the LA technique to heterogeneous samples usually requires preparing a homogeneous glass by fusing with lithium borate . A difficulty encountered with multi-element LA-ICP-MS analysis is the absence of standards... 

Minerals The main mineral constituents in milk are calcium and chlorine, magnesium chloride, phosphate, and citrate. Minerals in milk are mainly present as soluble salts or in colloidal form associated with caseins. Their concentrations may vary enormously. Thus, the minerals present in milk can be classified according to their concentration level as major and minor elements, with small quantitative contributions from trace and ultratrace elements. The total content of minerals in mammalian milks should correspond to the growth requirements of each biological species. Accordingly, the mineral total content in cow milk is four times higher than in human milk. 

For several of the ultratrace elements (Cr, Mo, and V), insufficient information is currently available as to the critical molecular species underlying their biological actions. Direct methods for determining total trace element concentrations in biological samples are therefore required. This can pose severe analytical difficulties, and may require specialist laboratory facilities, with appropriate techniques employed to reduce sample contamination. ... 

Essential and Toxic Effects of Macro-, Trace and Ultratrace Elements for Higher Plants, Interactions and Requirement... 

Three groups of essential mineral elements can be distinguished (Table 3.1). For convention and historical reasons, the elements are divided into macro, trace, and ultratrace elements. The animals requirement for macro elements is > 100 mg kg of food DM (dry matter), while that for trace and ultratrace... 

Factors which are important for the lowering of human health risks due to mineral deficiency and intoxication are the normative requirements of the macro, trace and ultratrace elements, recommendations for their intake, their apparent absorption and excretion rates, their interactions, tolerance limits for chemicals in food and water, and occupational health standards. 

The normative requirement of ultratrace elements is unknown, because their essentiality in humans has not yet been investigated. In experiments with animals, it was shown... 

Tab. 4.15 Requirement and tolerable daily intake of ultratrace elements...

GF-AAS methods combine a very high atomization efficiency with a 100-1000 fold increase in sensitivity compared to the conventional flame technique. For this reason and also because of the capability of handling solid samples as well as samples which normally requires sample pretreatment, GF-AAS is one of the most popular methods in trace and ultratrace element determinations in clinical chemistry. 

Trace elements, microelements elements required in very small quantities by living organisms. They act catalytically, or are components of catalytic systems. A elear distinction between T. e. and other mineral nutrients is not always possible, e.g. in the case of iron. A further classification into T. e. and ultratrace elements is sometimes used. 

In order to reach the interference-free limits of detection calculated by means of Eq. (1) and illustrated in Fig. 3 [6], it is necessary to eliminate other activities present in the sample using a radiochemical separation. This requires that the irradiated sample be decomposed, usually by the addition of nitric, perchloric, or sulfuric acids this does not create any blank problems but may easily result in losses of an ultratrace element to be determined. In order to control and minimize such losses a suitable amount of carrier of the element should always be added to the sample... 

TXRF extends EDXRF to a method for trace and ultratrace element analysis. A special feature is the small sample amount required, which is in the range ig-ng of a solid material and less than 100-10 pL of a liquid. Therefore, TXRF is a microanalysis method... 

In summary, application of ICP-MS in the semiconductor industry has expanded rapidly (and continues to expand), as the number of materials used in this field increases and the required monitoring concentration level decreases. The sample types that need to be analyzed have also spread widely from very clean samples, such as UPW, to difficult samples such as chemical mechanical polishing materials. The constant drive to produce ever smaller, ever cleaner microelectronic components, coupled with the continuing performance enhancement occurring in ICP-MS, ensures that this technology will remain at the forefront of ultratrace elemental analysis for several years to come. 

Trace elements are those elements of the periodic table that occur in animals or humans in amounts measured in mg per kg of body weight or less. The trace elements essential for health are usually required by humans in amounts measured in mg per day these elements include copper, iron, manganese, and zinc. The individual trace elements are discussed elsewhere in the encyclopedia. Since 1980, the term ultratrace element has appeared in the nutritional literature. Ultratrace elements have been defined as those elements with estimated dietary requirements usually less than Imgkg, and often less than 50pgkg of diet for laboratory animals. For humans, the term often is used to indicate an element with an established, estimated, or suspected requirement of less than 1 mg per day or generally indicated by pg per day. At least 18 elements could... 

As already mentioned, the ultra trace elements other than selenium and iodine are a disparate group in terms of their possible requirement or nutritional importance for human health and well-being. Although molybdenum has known essential functions, it has no unequivocally identified practical nutritional importance. The other 14 ultratrace elements discussed here have been suggested to be essential based on circumstantial evidence. This evidence is presented below along with some indication of possible requirement (extrapolated from the deficient animal intakes shown in Table 3), and some indication as to what constitutes a high intake. 

The requirements for the ultratrace elements will be met if a person consumes a diet based on the dietary guidelines recommended by. For some areas of the world, especially in developing countries where traditional, monotonous diets are based primarily on a cereal (particularly rice) or tuber staple, the intake of several ultratrace elements (e.g., boron, molybdenum) could possibly be low. Reported typical dietary intakes (mostly for industrialized countries) and rich sources of the ultratrace elements are shown in Table 3. 

The chemistry of rare earth elements makes them particularly useful in studies of marine geochemistry [637]. But the determination of rare earths in seawater at ultratrace levels has always been a difficult task. Of the various methods applied, instrumental neutron activation analysis and isotope dilution mass spectrometry were the main techniques used for the determination of rare earths in seawater. However, sample preparation is tedious and large amounts of water are required in neutron activation analysis. In addition, the method can only offer relatively low sample throughputs and some rare earths cannot be determined. The main drawbacks of isotopic dilution mass spectrometry are that it is time-consuming and expensive, and monoisotopic elements cannot be determined as well. 

Advantages High analysis rate 3-4 elements per hour Applicable to many more metals than voltammetric methods Superior to voltammetry for mercury and arsenic particularly in ultratrace range Disadvantages Nonspecific absorption Spectral interferences Element losses by molecular distillation before atomisation Limited dynamic range Contamination sensitivity Element specific (or one element per run) Not suitable for speciation studies in seawater Prior separation of sea salts from metals required Suspended particulates need prior digestion About three times as expensive as voltammetric equipment Inferior to voltammetry for cobalt and nickel... 

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